Seatbelt apparatus

ABSTRACT

A seatbelt retractor includes a spool formed into a hollow cylindrical shape and capable of winding a seatbelt onto a spool outer periphery or unwinding the seatbelt from the spool outer periphery. The retractor includes a motor accommodated in a cylindrical space of the spool and a motor speed-reduction mechanism configured to reduce the rotational speed of the motor via a plurality of gears. A controller is provided to control the operation of the motor.

BACKGROUND

The present invention relates to a technology for developing a seatbeltretractor to be installed in a vehicle.

Conventionally, a seatbelt apparatus is known, which is structured toprotect an occupant in a vehicle by a seatbelt (webbing) restraining theoccupant. For example, PCT international application No. 2003-507252(incorporated by reference herein) discloses a structure of a seatbeltretractor of a seatbelt apparatus, in which a spool (winding shaft) canbe rotated in a belt-winding direction or a belt-unwinding direction fora seatbelt by an electric motor.

SUMMARY

One embodiment of the invention relates to a seatbelt retractor. Theseatbelt retractor comprises a spool formed into a hollow cylindricalshape and capable of winding a seatbelt onto a spool outer periphery orunwinding the seatbelt from the spool outer periphery, a motoraccommodated in a cylindrical space of the spool and capable of rotatingthe spool in the belt winding direction or the belt unwinding direction;a motor speed-reduction mechanism configured to reduce the rotationalspeed of the motor via a plurality of gears between the driving shaft ofthe motor and the spool; and a control mechanism configured to controlthe operation of the motor. A motor housing of the motor extends in thewidth direction of the spool outer periphery such that the axialdirection of the motor coincides with the width direction of the spoolouter periphery. The ratio of the outside diameter D1 of the motorhousing relative to the outside diameter D2 of the spool outerperiphery, (D1/D2), is 0.8 or less.

Another embodiment of the invention relates to a seatbelt apparatus. Theseatbelt apparatus comprises a seatbelt retractor, and a seatbelt to beworn by a vehicle occupant seated in a seat. The seatbelt retractorcomprises a spool formed into a hollow cylindrical shape and capable ofwinding the seatbelt onto a spool outer periphery or unwinding theseatbelt from the spool outer periphery; a motor accommodated in acylindrical space of the spool and capable of rotating the spool in thebelt winding direction or the belt unwinding direction; a motorspeed-reduction mechanism configured to reduce the rotational speed ofthe motor via a plurality of gears between the driving shaft of themotor and the spool; and a control mechanism configured to control theoperation of the motor. A motor housing of the motor extends in thewidth direction of the spool outer periphery such that the axialdirection of the motor coincides with the width direction of the spoolouter periphery. The ratio of the outside diameter D1 of the motorhousing relative to the outside diameter D2 of the spool outer peripheryof the spool, (D1/D2), is 0.8 or less.

Another embodiment of the invention relates to a vehicle. The vehiclecomprises a seatbelt apparatus with a seatbelt retractor and a seatbeltto be worn by a vehicle occupant seated in a seat. The seatbeltretractor comprises a spool formed into a hollow cylindrical shape andcapable of winding the seatbelt onto a spool outer periphery orunwinding the seatbelt from the spool outer periphery; a motoraccommodated in a cylindrical space of the spool and capable of rotatingthe spool in the belt winding direction or the belt unwinding direction;a motor speed-reduction mechanism configured to reduce the rotationalspeed of the motor via a plurality of gears between the driving shaft ofthe motor and the spool; and a control mechanism configured to controlthe operation of the motor. A motor housing of the motor extends in thewidth direction of the spool outer periphery such that the axialdirection of the motor coincides with the width direction of the spoolouter periphery. The ratio of the outside diameter D1 of the motorhousing relative to the outside diameter D2 of the spool outer peripheryof the spool, (D1/D2), is 0.8 or less. The seatbelt apparatus isaccommodated in an accommodating space in the vehicle.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory only,and are not restrictive of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become apparent from the following description, appendedclaims, and the accompanying exemplary embodiments shown in thedrawings, which are briefly described below.

FIG. 1 shows a schematic structure of a seatbelt apparatus, which isinstalled in a vehicle, according to an embodiment of the presentinvention.

FIG. 2 is a sectional view of a retractor shown in FIG. 1.

FIG. 3 is a sectional view on arrows of a line A-A of the retractorshown in FIG. 2.

DETAILED DESCRIPTION

The technology described in PCT international application No.2003-507252 gives us a possibility of using an electric motor to conductthe action of the spool for winding or unwinding the seatbelt, as astructure of the seatbelt retractor. With regard to the design of suchseatbelt apparatuses, further technical requirement exists for reducingthe size of the seatbelt retractor to correspond to the configuration ofa pillar or the like as a narrow space for accommodating the seatbeltretractor.

Therefore, embodiments of the present invention have been made in viewof the above requirement and it is an object of the present invention toprovide a technology effective for the miniaturization of a seatbeltretractor to be installed in a vehicle.

Embodiments of the present invention can be typically adapted to aseatbelt retractor to be installed in a vehicle. Embodiments of thepresent invention can be applied to a technology for a seatbeltretractor to be installed in a vehicle other than the vehicle.

The seatbelt retractor of a first embodiment comprises at least a spool,a motor, a motor speed-reduction mechanism, and a control mechanism.

The spool of this embodiment is a member which is formed into a hollowcylindrical shape and is capable of winding a seatbelt onto a spoolouter periphery thereof or unwinding the seatbelt from the spool outerperiphery. The spool outer periphery is adapted to be a surface withwhich the seatbelt is in contact. The seatbelt is a long belt to be wornby a vehicle occupant seated in a seat and is sometimes called“webbing”. Typically, the vehicle occupant seated in the vehicle seat isrestrained by the seatbelt when restraint is required such as a vehiclecollision, thereby ensuring the protection of the vehicle occupant.

The motor of this embodiment is a motor which is accommodated in thecylindrical space of the spool and has a function of rotating the spoolin the belt winding direction or the belt unwinding direction.

The motor speed-reduction mechanism has a function of reducing therotational speed of the motor via a plurality of gears between thedriving shaft of the motor and the spool.

The control mechanism of this embodiment is a mechanism for controllingthe operation (the rotational speed, the rotational direction) of themotor. The control mechanism is typically composed of a CPU (centralprocessing unit), an input/output unit, a storage unit, a peripheralunit, and the like.

In this embodiment, a motor housing of the motor extends in the axialdirection which is equal to the width direction of the spool outerperiphery of the spool in the state that the motor is accommodated andthe ratio of the outside diameter D1 of the motor housing relative tothe outside diameter D2 of the spool outer periphery of the spool,(D1/D2), is set to be 0.8 or less. Since the size of the seatbeltretractor in the width direction, the size of the motor housing of theaxial direction, and the size of the spool outer periphery of the spoolin the width direction are equal to each other, the reduction in sizeand the reduction in weight of the retractor can be achieved by suitablysetting the relative size relating to the radial direction (proportionin outside diameter) between the motor and the spool.

According to the structure of this embodiment in which the spool isrotated by the motor, a spring mechanism for biasing the spool in thebelt winding direction can be eliminated. The spring mechanism isgenerally located adjacent to the spool in the width direction of thespool. Therefore, the elimination of the spring mechanism reduces thesize relating to the width direction of the spool, thereby enabling thefurther reduction in overall size of the seatbelt retractor.

According to the structure of this embodiment in which the motor isaccommodated in the cylindrical space of the spool, the reduction insize and the reduction in weight of the seatbelt retractor are achievedand, in addition, the noise insulation and the electromagnetic-waveshielding in the operation of the motor are improved.

In the seatbelt retractor of a second embodiment, the ratio (D1/D2) asin the first embodiment is set to satisfy 0.7≦(D1/D2)≦0.75. Thisstructure enables to further reduce the size and the weight of theseatbelt retractor. In another embodiment, the ratio can be in the rangeof 0.75 to 0.79. In another embodiment, the ratio can be in the range of0.6 to 0.75.

In the seatbelt retractor of a third embodiment, the gears of the motorspeed-reduction mechanism as in the first or second embodiment arearranged to extend on the same plane perpendicular to the axialdirection of the motor housing. According to this structure, the sizerelating to the axial direction of the motor speed-reduction mechanismcan be reduced by arrangement of the plural gears, thereby furtherreducing the overall size relating to the axial direction of theretractor including the motor speed-reduction mechanism. Therefore, thefurther reduction in size of the seatbelt retractor to be installed inthe vehicle is achieved.

The seatbelt retractor of a fourth embodiment has the same or similarstructure as in any one of the first through third embodiments and isadapted such that the spool and the motor housing are supported by eachother via at least a bearing mechanism disposed between the innerperiphery of the spool and the outer periphery of the motor housing. Forcomposing the suitable bearing structure, the present invention allowsthe adoption of another bearing mechanism in addition to the bearingmechanism disposed between the inner periphery of the spool and theouter periphery of the motor housing, if necessary. According to thisstructure, the rotation of the spool relative to the motor housing isallowed by the bearing structure with simple structure.

The seatbelt retractor of a fifth embodiment has the same or similarstructure as in any one of the first through fourth embodiments and isadapted to have such dimensions as to be used for a passenger in a rearseat of a vehicle. According to this structure, a seatbelt retractorhaving reduced size is provided. The seatbelt retractor having theaforementioned dimensional structure can be accommodated in a relativelynarrow area in a vehicle for the purpose of use by a passenger in a rearseat of a vehicle. Though the seatbelt retractor has reduced size forthe passenger in the rear seat, the seatbelt retractor can be, ofcourse, accommodated in the vehicle for the purpose of use by a driveror a passenger in a front seat.

The seatbelt retractor of a sixth embodiment has the same or similarstructure as in any one of the first through the fourth embodiments andis adapted to be accommodated in an accommodating space in a rear pillarof a vehicle which is located on the rear side of the A-pillar of thevehicle. The “rear pillar” used here corresponds to a B-pillar or aC-pillar in case of a vehicle having two rows of seats or corresponds toa B-pillar, a C-pillar, or a D-pillar in case of a vehicle having threerows of seats. This structure enables to provide a compact seatbeltretractor which can be accommodated in the accommodating space of therear pillar of which size is limited.

The seatbelt retractor of a seventh embodiment has the same or similarstructure as in any one of the first through fourth embodiments and isadapted to be accommodated in an accommodating space in a seat of avehicle. The “seat” used here widely includes a driver's seat and apassenger's seat in a first-row, and second- and third-row seats. Thisstructure enables to provide a compact seatbelt retractor which can beaccommodated in the accommodating space of the seat of which size islimited.

The seatbelt retractor of an eighth embodiment has the same or similarstructure as in the sixth or seventh embodiments and is adapted suchthat, in the state that the seatbelt retractor is accommodated in theaccommodating space, the spool outer periphery of the spool extends inthe longitudinal direction of a vehicle, and the size of the spool outerperiphery in the width direction and the size of the accommodating spacein the rear pillar or the accommodating space in the seat in thelongitudinal direction of the vehicle are equal to each other. Thisstructure enables to provide a compact seatbelt retractor which can beaccommodated in the accommodating space in the rear pillar of which sizeis limited in the longitudinal direction of the vehicle or in theaccommodating space of the seat of which size is limited.

A seatbelt apparatus of a ninth embodiment is a seatbelt apparatuscomprising at least a seatbelt retractor as in any one of the firstthrough eighth embodiments, and a seatbelt to be worn by a vehicleoccupant seated in a seat and which can be wound onto or unwound from aspool outer periphery of a spool of the seatbelt retractor.

According to this structure, the reduction in size and the reduction inweight of the seatbelt retractor enable the reduction in size and thereduction in weight of the seatbelt apparatus to be installed in thevehicle. Accordingly, the degree of freedom of location of the seatbeltapparatus in the vehicle is increased.

A vehicle with a seatbelt apparatus of a tenth embodiment is a vehiclein which the seatbelt apparatus is that of the ninth embodiment and isaccommodated in an accommodating space in a vehicle such as anaccommodating space in a pillar, an accommodating space in a seat, or anaccommodating space in another part of the vehicle. This structureenables to provide a vehicle in which a miniaturized seatbelt apparatusis accommodated in an accommodating space in the vehicle.

As described in the above, embodiments of the present invention canprovide a technology, particularly relating to the structure of aseatbelt retractor, which is effective for the reduction in overall sizeof the seatbelt retractor to be installed in a vehicle. According to thetechnology, the overall size of the seatbelt retractor is reduced bysuitably setting the relative size relating to the radial direction(proportion in the outside diameter) between a motor and a spool.

Hereinafter, embodiments of the present invention will be described indetail with reference to drawings. First, description will be made asregard to the structure of a seatbelt apparatus 100 as one ofembodiments of “seatbelt apparatus” according to the present inventionwith reference to FIG. 1 through FIG. 3.

The schematic structure of the seatbelt apparatus 100, which isinstalled in a vehicle, of the embodiment according to the presentinvention is shown in FIG. 1.

As shown in FIG. 1, the seatbelt apparatus 100 of this embodiment is aseatbelt apparatus for a vehicle to be installed in an automotivevehicle as “a vehicle with a seatbelt apparatus” and mainly consists ofa seatbelt 110, a retractor 130, and an ECU 150. In addition, an inputelement 170 is installed in the vehicle to detect information aboutcollision prediction or collision occurrence of the vehicle, informationabout the driving state of the vehicle, information about the sittingposition and the body size of a vehicle occupant seated in a vehicleseat, information about traffic conditions around the vehicle,information about weather condition and about time zone, and the likeand to input such detected information to the ECU 150. The detectedinformation of the input element 170 is transmitted to the ECU 150anytime or at predetermined intervals and is used for the operationcontrol of the seatbelt apparatus 100 and the like.

The seatbelt 110 is a long belt (webbing) to be used for restraining andcanceling the restraint of a vehicle occupant C seated in a vehicle seat10 as a driver's seat (corresponding to the “seat” of embodiments of thepresent invention). The seatbelt 110 is withdrawn from the retractor 130fixed to the vehicle and extends through a deflection fitting 111provided around an area about the shoulder of the vehicle occupant C andis connected to an outer anchor 114 through a tongue 112. The deflectionfitting 111 has a function of holding the seatbelt 110 to the area aboutthe shoulder of the occupant C and guiding the seatbelt 110. Byinserting the tongue 112 to a buckle 116 fixed to the vehicle body, theseatbelt 110 becomes into the state worn by the vehicle occupant C. Theseatbelt 110 corresponds to the “seatbelt” of embodiments of the presentinvention.

The retractor 130 is a device capable of performing the action ofwinding or unwinding the seatbelt 110 by a spool 132 as will bedescribed later and corresponds to the “seatbelt retractor” ofembodiments of the present invention. The retractor 130 is installed inan accommodating space in a B-pillar 12 of the vehicle in the embodimentshown in FIG. 1.

The ECU 150 has a function of conducting the control of the retractor130 and other operational mechanisms based on the input signals from theinput element 170 and comprises a CPU (Central processing unit), aninput/output unit, a storage unit, a peripheral unit, and the like.Particularly in this embodiment, the ECU 150 controls a motor 133, aswill be described later, of the retractor 130. Specifically, the ECU 150controls the amount of electricity supplied to an electromagnetic coil(value of current and value of voltage in the electromagnetic coil) ofthe motor 133 and the direction of the electricity (energizationdirection in the electromagnetic coil) so as to vary the rotationalspeed or the rotational direction of a shaft of the motor 133. The ECU150 corresponds to the “control mechanism” of the present invention.

Referring to FIG. 2 and FIG. 3, the retractor 130 will be described indetail. FIG. 2 is a sectional view of the retractor 130 shown in FIG. 1and FIG. 3 is a sectional view on arrows of a line A-A of the retractor130 shown in FIG. 2.

As shown in FIG. 2, the retractor 130 of this embodiment comprises abase frame (retractor body frame) 131, which is fixed to the vehiclebody, and further comprises the spool (winding shaft) 132, the motor133, a Hall sensor 134, a magnetic disc 135, an internal gear 136,planetary gears 137, a sun gear 138, a carrier 139, and bearings 140,141 which are assembled to the base frame 131.

The spool 132 of the retractor 130 is a member rotatably supported tothe base frame 131 and corresponds to the “spool” of embodiments of thepresent invention. Specifically, the bearing 140 lies between the spool132 and the internal gear 136 which is a fixed member and the bearing141 lies between the spool 132 and the body of the motor 133 which is afixed member, whereby the spool 132 is rotatable relative to the fixedmembers. That is, the spool 132 and a motor housing 133 a of the motor133 are supported by each other via the bearing mechanism (bearing 140)disposed between the outside surface of the spool and the inside surfaceof the internal gear and the bearing mechanism (bearing 141) disposedbetween the inner periphery of the spool and the outer periphery of themotor housing. According to this structure, the rotation of the spool132 relative to the motor housing 133 a is allowed by simple bearingstructure.

In the retractor 130, the seatbelt 110 is wound onto a spool outerperiphery 132 a of the spool 132 or the seatbelt 110 is unwound from thespool outer periphery 132 a of the spool 132. That is, the spool outerperiphery 132 a of the spool 132 is a surface with which the seatbelt110 is in contact. The shaft of the motor 133 is rotated in onedirection so as to conduct operation of unwinding the seatbelt 110 fromthe spool 132, while the shaft of the motor 133 is rotated in the otherdirection so as to conduct operation of winding the seatbelt 110 ontothe spool 132. Details about this will be described later.

According to the structure of rotating the spool 132 by the motor 133such as this embodiment, a spring mechanism for biasing the spool 132 inthe belt winding direction can be eliminated. The spring mechanism isgenerally located adjacent to the spool 132 in the width direction ofthe spool 132. Therefore, the elimination of the spring mechanismreduces the size relating to the width direction of the spool 132,thereby enabling the reduction in overall size of the retractor 130.

The spool 132 is formed into a hollow cylindrical shape of which one endis closed and the other end is open. The motor 133 is inserted into of acylindrical hollow space 132 b through the open end and is accommodatedin the hollow space 132 b. In the state that the motor 133 isaccommodated in the hollow space 132 b of the spool 132, the motorhousing 133 a of the motor 133 extends along the axial direction of themotor 133 which extends along the width direction of the spool outerperiphery 132 a of the spool 132.

In the state that the motor 133 is accommodated, three dimensions, i.e.,the size L1 of the motor housing 133 a of the motor 133 in the axialdirection, the size L2 of the spool outer periphery 132 a of the spool132 in the width direction, and the width of the seatbelt 110, are equalto each other. That is, in this embodiment, the size of the motorhousing 133 a in the axial direction and the size of the spool outerperiphery 132 a in the width direction are set to correspond to thestandard width of the seatbelt 110. As shown in FIG. 2, in thisembodiment, the overall size of the spool 132 in the width direction isnearly equal to the size of the spool outer periphery 132 in the widthdirection. That is, the four dimensions, i.e. the overall size of thespool 132 in the width direction, the size L1 of the motor housing 133 ain the axial direction, the size L2 of the spool outer periphery 132 ain the width direction, and the width of the seatbelt 110 are equal toeach other.

According to this structure, the width of the spool 132 can be reducedto correspond to the size of the motor housing 133 a in the axialdirection, thereby reducing the overall size relating to the axialdirection of the retractor 130. Therefore, the miniaturization of theretractor 130 and the seatbelt apparatus 100 to be installed in thevehicle is achieved, thereby increasing the degree of freedom oflocation of the seatbelt retractor 130 and the seatbelt apparatus 100 inthe vehicle. The motor housing 133 a is designed to have the maximumsize in the axial direction within the range of the width of the spool132, allowing the use of a motor with higher output.

According to the structure of this embodiment that the motor 133 isaccommodated in the cylindrical space of the spool 132, the reduction insize and the reduction in weight of the retractor 130 are achieved and,in addition, the noise insulation and the electromagnetic-wave shieldingin the operation of the motor are improved.

In this embodiment, the ratio of the outside diameter D1 of the motorhousing 133 a of the motor 133 relative to the outside diameter D2 ofthe spool outer periphery 132 a of the spool 132, i.e. D1/D2, ispreferably set to be 0.8 or less, particularly set to satisfy0.7≦D1/D2)≦0.75. The ratio (D1/D2) can be suitably set within a range of(D1/D2)≦0.8, particularly within a range of 0.7≦(D1/D2)≦0.75. Forexample, the outside diameter D1 of the motor 133 may be 40 (mm) and theoutside diameter D2 of the spool outer periphery 132 a of the spool 132may be 55 (mm). In this case, the ratio (D1/D2) is about 0.73. Accordingto this structure, the size of the spool 132 in the radial direction canbe reduced to correspond to the size of the motor 133 in the radialdirection, thereby enabling the reduction in overall size relating tothe radial direction of the retractor 130.

Further, the spool 132 of this embodiment defines the substantial outerprofile of the retractor 130 and forms a “seatbelt retractor housing” inwhich at least main components of the spool such as the motor 133 areaccommodated. In this embodiment, the correlation among the volume V1 ofthe motor housing 133 a of the motor 133 (i.e., volume occupied by themotor housing 133 a), the volume V2 of the cylinder portion of the spool132, and the storage volume V3 within the seatbelt retractor housing isset to achieve the equation V3<V1+V2. In this embodiment, the volume V2of the spool 132 substantially coincides with the storage volume V3within the seatbelt retractor housing. The storage volume V3 within theseatbelt retractor housing is defined as the volume of the inner spaceof a roll formed by the seatbelt in the wound-up state. The settingrange of these volume is defined as a retractor miniaturizationadjustment range effective for reducing the size of the seatbeltretractor, taking the volumes relative to the spool and the motor intoconsideration. It is further preferable to achieve the equationV3<(V1+V2)×N, wherein 0.5<N<1. For securely achieving the reduction insize and the reduction in weight of the retractor, the N in V3<(V1+V2)×Nis preferably in a range of 0.55<N<0.95, more preferably 0.55<N<0.85,especially preferably 0.55<N<0.75.

In this embodiment, the ratio (V1/V2) of the volume V1 of the motorhousing 133 a of the motor 133 (i.e., volume occupied by the motorhousing 133 a) to the volume V2 of the cylinder portion of the spool 132is set to be within a retractor miniaturization adjustment range(corresponding to the “retractor miniaturization adjustment range” ofembodiments of the present invention) about the volume ratio in whichthe ratio (V1/V2) is 40 percent (about 0.4) or more and less than 100percent (about 1).

The retractor miniaturization adjustment range as mentioned above isdefined as a range effective for reducing the size of the seatbeltretractor 130, taking the volumes relative to the spool 132 and themotor of this embodiment into consideration. Specifically, as shown inFIG. 2, the size of the retractor 130 in the width direction is equal tothe size L1 of the motor housing 133 a in the axial direction and thesize L2 of the spool outer periphery 132 a of the spool 132 in the widthdirection. Therefore, by suitably setting the relative sizes of thespool 132 and the motor 133 in the radial direction, the relationshipamong the respective volumes corresponding to the retractorminiaturization adjustment range is substantially set. According to thisstructure, the miniaturization of the retractor is achieved. Theseatbelt retractor 130 having the aforementioned dimensional structureaccording to this embodiment can be accommodated in a relatively narrowarea of a vehicle for the purpose of use by a passenger in a rear seatof a sedan-type vehicle. Though the seatbelt retractor 130 has reducedsize for the passenger in the rear seat, the seatbelt retractor 130 canbe, of course, accommodated in the vehicle for the purpose of use by adriver or a passenger in a front seat.

The motor 133 of this embodiment is an electric motor of a type,so-called “brushless motor of inner rotor type”. The motor 133corresponds to the “motor” of the present invention. The motor 133 usesa magnet as a rotor and a coil as a stator which are accommodated in themotor housing 133 a. The stator is disposed around the rotor. The motor133 is structured such that the motor shaft is rotated according to therotation of the rotor. In the motor 133, the Hall sensor (a magneticposition detector) 134 is mounted on a side of the motor housing 133 aand the magnetic disc 135 is mounted on a side of the rotor. The Hallsensor 134 and the magnetic disc 135 cooperate together to detect theposition of the rotor. From the information of the detection, the amountof winding or unwinding the seatbelt 110 is obtained. Based on theamount of winding or unwinding of the seatbelt 110, the rotational speedof the motor and the load of the motor can be controlled. In thisembodiment, as mentioned above, a mechanism for detecting the positionof the rotor in the motor 133 are also used as a mechanism for detectingthe amount of winding or unwinding the seatbelt 110. Therefore, the useof the brushless motor such as the motor 133 can eliminate sensors forexclusive use of detecting the rotational speed and rotational directionof the rotor and of detecting the amount of winding or unwinding theseatbelt 110. This also provides economical advantage. The brushlessmotor such as the motor 133 is effective for reducing the size of thebody, improving the output, and improving the heat radiation property.

As shown in FIG. 2 and FIG. 3, the shaft of the motor 133 is adapted tohave the sun gear 138. Three planetary gears 137 mesh with the outerperiphery of the sun gear 138. The outer peripheries of the planetarygears 137 mesh with inner periphery of the internal gear 136. That is, agear train, so-called “planetary gear mechanism” is constructed in whichthe planetary gears 137 are arranged between the internal gear 136 andthe sun gear 138. The internal gear 136 is fixed to the base frame 131.The planetary gears 137 are rotatably supported by the carrier 139 andthe spool 132 is connected to the carrier 139. The internal gear 136,the planetary gears 137, the sun gear 138 compose together aspeed-reduction mechanism (corresponding to the “motor speed-reductionmechanism” of embodiments of the present invention) of the motor 133. Inthis embodiment, the motor speed-reduction mechanism is located adjacentto the motor housing 133 a relative to the axial direction of the motorhousing 133 a. Further in this embodiment, the plural gears composingthe motor speed-reduction mechanism are arranged to extend on the sameplane in a direction perpendicular to the axial direction of the shaftof the motor. According to the structure, the size relating to the axialdirection of the motor speed-reduction mechanism can be reduced byarrangement of the plural gears, thereby further reducing the overallsize relating to the axial direction of the retractor 130 including themotor speed-reduction mechanism. Therefore, the reduction in size of theretractor 130 and the seatbelt apparatus 100 to be installed in thevehicle is achieved.

In this embodiment, the three dimensions, i.e. the first size relatingto the width direction of the spool outer periphery 132 a, the secondsize which is the size relating to the axial direction of the motorhousing 133 a plus the size relating to the axial direction of the motorspeed-reduction mechanism, and the width of the seatbelt 110 are equalto each other. That is, in this embodiment, the first size and thesecond size are set to correspond to the standard width of the seatbelt110. As shown in FIG. 2, in this embodiment, the overall size of thespool 132 in the width direction is nearly equal to the size of thespool outer periphery 132 a in the width direction. That is, the fourdimensions, i.e. the overall size of the spool 132 in the widthdirection, the first size, the second size, and the width of theseatbelt 110 are equal to each other. According to this structure, thewidth of the spool 132 can be reduced to correspond to the size of thecombination of the motor housing 133 a with the motor speed-reductionmechanism in the axial direction, thereby reducing the overall sizerelating to the axial direction of the seatbelt retractor.

In this embodiment, the driving shaft (motor shaft) as the rotationalaxis of the motor 133, the spool shaft as the rotational axis of thespool 132, the speed-reduction shaft as the rotational axis of the sungear 138 as one component of the speed-reduction mechanism are generallyaligned in a straight line along the width direction of the spool outerperiphery 132 a. According to the structure, the simplification andminiaturization of the motor speed-reduction mechanism are achieved andthe sizes relating to the radial direction of the motor 133, the spool132, and the motor speed-reduction mechanism are reduced, therebyenabling the reduction in overall size and weight of the retractor.

In the aforementioned structure of the retractor 130, as the shaft ofthe motor 133 is rotated, the three planetary gears 137 meshing with thesun gear 138 move around the speed-reduction shaft of the sun gear 138(the driving shaft of the motor 133), whereby the spool 132 rotates viathe carrier 139. For example, when the sun gear 138 rotates about thespeed-reduction shaft in the clockwise direction in FIG. 3, the threeplanetary gears 137 rotate about their axes in the counterclockwisedirection and move around the sun gear 138 in the clockwise directionbetween the external teeth of the sun gear 138 and the internal teeth ofthe internal gear 136. On the other hand, when the sun gear 138 rotatesabout the speed-reduction shaft in the counterclockwise direction, thethree planetary gears 137 rotate about their axes in the clockwisedirection and move around the sun gear 138 in the counterclockwisedirection between the external teeth of the sun gear 138 and theinternal teeth of the internal gear 136. During this, the rotation ofthe motor 133 is transmitted to the spool 132 while the rotational speedis reduced to some fraction of the rotational speed of the motor and thetorque is increased. By the rotational torque transmitted to the spool132, the seatbelt 110 is wound onto or unwound from the outer peripheryof the spool 132. According to this structure, the motor speed-reductionmechanism is simplified, thereby enabling the reduction in overall sizeand weight of the retractor.

In the seatbelt apparatus 100 having the aforementioned structure, thecontrol of the operation of the motor 133 of the retractor 130 is usedwhen the restraint of the vehicle occupant is conducted or when therestraint of the vehicle occupant is cancelled. The control is suitablyconducted by the ECU 150 based on the input signals from the inputelement 170 shown in FIG. 1. That is, the seatbelt apparatus 100 of thisembodiment has such a function that, based on the input signals from theinput element 170, the ECU 150 controls the operation of the motor 133to adjust the tension of the seatbelt 110 so as to control the conditionabout the restraint of the vehicle occupant and therefore composes anoccupant restraining system for a vehicle. Specifically, the followingfirst through fifth modes may be employed.

In the first mode (putting-on mode), the motor 133 is controlled to berotated in the belt unwinding direction to facilitate the vehicleoccupant to withdraw the seatbelt when the vehicle occupant inserts andlatches the tongue 112 to the buckle 116 of the seatbelt 110 by his orher hand. Accordingly, the load and operation for withdrawing theseatbelt can be relieved.

In the second mode (fitting mode), the motor 133 is controlled to berotated in the belt winding direction to apply predetermined tension onthe seatbelt 1 10 in the state that the seatbelt is worn by the vehicleoccupant. Accordingly, slack of the seatbelt generated when the seatbeltis withdrawn can be eliminated. If necessary, the motor 133 may becontrolled to rotate a little in the belt winding direction or the beltunwinding direction to conduct fine adjustment for controlling comfortof the vehicle occupant wearing the seatbelt.

In the third mode (pre-rewinding (restraining) mode), the motor 133 iscontrolled to rotate in the belt winding direction to apply strongtension on the seatbelt 110 when the seatbelt is worn by the vehicleoccupant. Accordingly, change in posture of the vehicle occupant due toa vehicle collision or emergency braking is inhibited so as to ensurethe protection of the vehicle occupant.

In the fourth mode (warning mode), when danger or collision is predictedin the state the seatbelt is used, the motor 133 is controlled to rotatein the belt winding direction or the belt unwinding direction to changetension on the seatbelt 110 so as to urge the vehicle occupant to payattention. For example, the operation of applying strong tension andweak tension onto the seatbelt 110 is repeated, thereby preventing thevehicle occupant from dozing and thus ensuring the collision prevention.

In the fifth mode (storing mode), the motor 133 is controlled to rotatein the belt winding direction to facilitate the vehicle occupant tostore the seatbelt 110 after the vehicle occupant releases the latchingof the tongue 112 from the buckle 116. Accordingly, the load andoperation for storing the seatbelt can be relieved.

The present invention is not limited to the aforementioned embodiment,various variations and modifications may be made. For example, thefollowing embodiments as variations of the aforementioned embodiment maybe carried out.

Though the retractor 130 described in the above embodiment is used forthe vehicle occupant seated in the driver's seat and is accommodated inthe accommodating space in the B-pillar, embodiments of the presentinvention can be adopted to the structure of retractors for vehicleoccupants seated in a passenger's seat and a rear seat. When embodimentsof the present invention are adopted to the structure of a retractor fora vehicle occupant seated in the rear seat, the retractor isaccommodated in an accommodating space in a C-pillar in case of avehicle of a type having two rows of seats or the retractor isaccommodated in an accommodating space in a C-pillar or a D-pillar incase of a vehicle of a type having three rows of seats. Theaccommodating space in the C-pillar or the D-pillar is often limited inthe longitudinal direction of the vehicle. Especially in such case, aretractor having reduced size in the width direction such as theretractor 130 in the embodiment is effective.

Though the above embodiment has been described with regard to the casethat the retractor 130 is accommodated in the accommodating space in thepillar, embodiments of the present invention can be adapted to thestructure in which the retractor is accommodated in an accommodatingspace in a member other than the pillar. For example, a vehicle seatsuch as a driver's seat or a passenger's seat as a first-row seat, or aseat as a second- or third-row seat may be provided with anaccommodating space inside thereof and the retractor 130 of theembodiment can be accommodated in the accommodating space inside theseat. The size of the seat is often limited in the longitudinaldirection of the vehicle similarly to the vehicle pillar. Especially inthis case, a retractor having reduced size in the width direction suchas the retractor 130 in the embodiment is effective.

Though the above embodiment has been described with regard to thestructure of the seatbelt apparatus to be installed in a vehicle,embodiments of the present invention can be adopted to seatbeltapparatuses to be installed in a wide variety of vehicles other thanautomobiles, such as aircraft, boats, and trains.

Japan Priority Application 2004-350440, filed Dec. 2, 2004 including thespecification, drawings, claims and abstract, is incorporated herein byreference in its entirety.

Given the disclosure of the present invention, one versed in the artwould appreciate that there may be other embodiments and modificationswithin the scope and spirit of the invention. Accordingly, allmodifications attainable by one versed in the art from the presentdisclosure within the scope and spirit of the present invention are tobe included as further embodiments of the present invention. The scopeof the present invention is to be defined as set forth in the followingclaims.

1. A seatbelt retractor comprising: a spool formed into a hollowcylindrical shape and capable of winding a seatbelt onto a spool outerperiphery or unwinding the seatbelt from the spool outer periphery,motor accommodated in a cylindrical space of the spool and capable ofrotating the spool in the belt winding direction or the belt unwindingdirection; a motor speed-reduction mechanism configured to reduce therotational speed of the motor via a plurality of gears between thedriving shaft of the motor and the spool; and a control mechanismconfigured to control the operation of the motor, wherein a motorhousing of the motor extends in the width direction of the spool outerperiphery such that the axial direction of the motor coincides with thewidth direction of the spool outer periphery, and wherein the ratio ofthe outside diameter D1 of the motor housing relative to the outsidediameter D2 of the spool outer periphery, (D1/D2), is 0.8 or less. 2.The seatbelt retractor as claimed in claim 1, wherein the ratio (D1/D2)is set to satisfy 0.7≦((D1/D2)≦0.75.
 3. The seatbelt retractor asclaimed in claim 1, wherein the ratio (D1/D2) is in the range of 0.75 to0.79
 4. The seatbelt retractor as claimed in claim 1, wherein the ratio(D1/D2) is in the range of 0.6 to 0.75.
 5. The seatbelt retractor asclaimed in claim 1, wherein the plurality of gears of the motorspeed-reduction mechanism are arranged to extend on the same planeperpendicular to the axial direction of the motor housing.
 6. Theseatbelt retractor as claimed in claim 1, wherein the spool and themotor housing are supported by each other via a bearing mechanismdisposed between the inner periphery of the spool and the outerperiphery of the motor housing.
 7. The seatbelt retractor as claimed inclaim 1, wherein the seatbelt retractor is adapted to have suchdimensions as to be used for a passenger in a rear seat of a vehicle. 8.The seatbelt retractor as claimed in claim 1, wherein the seatbeltretractor is adapted to be accommodated in an accommodating space in apillar of a vehicle which is located on the rear side of the A-pillar ofthe vehicle.
 9. The seatbelt retractor as claimed in claim 8, wherein inthe state that the seatbelt retractor is accommodated in theaccommodating space, the spool outer periphery of the spool extends inthe longitudinal direction of a vehicle, and the length of the spoolouter periphery in the width direction and the length of theaccommodating space in the longitudinal direction of the vehicle areequal to each other.
 10. The seatbelt retractor as claimed in claim 1,wherein the seatbelt retractor is adapted to be accommodated in anaccommodating space in a seat of a vehicle.
 11. The seatbelt retractoras claimed in claim 10, wherein in the state that the seatbelt retractoris accommodated in the accommodating space, the spool outer periphery ofthe spool extends in the longitudinal direction of a vehicle, and thelength of the spool outer periphery in the width direction and thelength of the accommodating space in the longitudinal direction of thevehicle are equal to each other.
 12. A seatbelt apparatus comprising: aseatbelt retractor, and a seatbelt to be worn by a vehicle occupantseated in a seat, wherein the seatbelt retractor comprises: a spoolformed into a hollow cylindrical shape and capable of winding theseatbelt onto a spool outer periphery or unwinding the seatbelt from thespool outer periphery; a motor accommodated in a cylindrical space ofthe spool and capable of rotating the spool in the belt windingdirection or the belt unwinding direction; a motor speed-reductionmechanism configured to reduce the rotational speed of the motor via aplurality of gears between the driving shaft of the motor and the spool;and a control mechanism configured to control the operation of themotor, wherein a motor housing of the motor extends in the widthdirection of the spool outer periphery such that the axial direction ofthe motor coincides with the width direction of the spool outerperiphery, and wherein the ratio of the outside diameter D1 of the motorhousing relative to the outside diameter D2 of the spool outer peripheryof the spool, (D1/D2), is 0.8 or less.
 13. A vehicle, comprising: aseatbelt apparatus with a seatbelt retractor and a seatbelt to be wornby a vehicle occupant seated in a seat, wherein the seatbelt retractorcomprises: a spool formed into a hollow cylindrical shape and capable ofwinding the seatbelt onto a spool outer periphery or unwinding theseatbelt from the spool outer periphery; a motor accommodated in acylindrical space of the spool and capable of rotating the spool in thebelt winding direction or the belt unwinding direction; a motorspeed-reduction mechanism configured to reduce the rotational speed ofthe motor via a plurality of gears between the driving shaft of themotor and the spool; and a control mechanism configured to control theoperation of the motor, wherein a motor housing of the motor extends inthe width direction of the spool outer periphery such that the axialdirection of the motor coincides with the width direction of the spoolouter periphery, wherein the ratio of the outside diameter D1 of themotor housing relative to the outside diameter D2 of the spool outerperiphery of the spool, (D1/D2), is 0.8 or less, and wherein theseatbelt apparatus is accommodated in an accommodating space in thevehicle.